Communicable/Infectious Diseases

Myth There isn’t much a person can do to avoid spreading or catching a cold or the flu. Fact About 80% of infectious diseases are spread by hand contact. Washing your hands with soap and water is a simple and effective way to prevent the spread of colds and the flu. Do you think most teens wash their hands as much as they should? What do you think are some ways to encourage more frequent hand washing?

Communicable Diseases (first note) Communicable diseases, also know as infectious diseases are caused by organisms or viruses that enter and multiply within the human body. Microorganisms are organisms that can be seen only through a microscope. Microorganisms and viruses that cause disease are called pathogens. Pathogens can cause an infectious disease when they enter your body and multiply.

Bacteria Bacteria (bak TEER ee uh) are simple, single-celled microorganisms. Bacteria live in air, soil, food, and in and on the bodies of plants and animals, including you. Some bacteria injure cells by giving off poisons called toxins (TAHK sinz).

Viruses The smallest pathogens are viruses. A virus can multiply only after entering a living cell. The virus then takes over the cell’s reproductive mechanisms, resulting in cell damage or death.

Fungi Organisms such as yeasts, molds, and mushrooms are known as fungi (FUN jy). Fungi grow best in warm, dark, moist areas.

Protozoans Single-celled organisms that are much larger and more complex than bacteria are known as protozoans (proh tuh ZOH unz). Protozoans have the ability to move through fluids in search of food.

How Pathogens Are Spread Pathogens can spread through contact with an infected person an infected animal contaminated objects contaminated food contaminated soil contaminated water The pathogens can then enter the body through breaks in the skin or through the moist linings of the eyes, ears, nose, mouth, or other openings.

Infected People Many infectious diseases are spread through some form of contact with a person who has the disease. The contact may be direct physical contact. Infectious diseases can also spread through indirect contact.

Infected Animals Some infectious diseases are transmitted to humans through the bites of animals.

Contaminated Objects Some pathogens can survive for a period of time outside a person’s body. These pathogens can be spread from person to person on objects such as doorknobs eating utensils towels needles used for body piercings and tattoos

Contaminated Food, Soil, or Water Some pathogens are naturally present in food and soil. Sometimes water and food become contaminated with pathogens from infected people.

Your Body’s Physical and Chemical Defenses Saliva and tears Saliva and tears can wash away some pathogens. Stomach acid When you swallow certain pathogens with food, water, or mucus, acids in your stomach can kill those pathogens. 1 Mucous membranes Mucus traps some pathogens, preventing them from entering your body. 2 3 Cilia Cilia help move mucus and pathogens out of your body when you cough or sneeze. 4 Skin Your skin is an effective barrier against many pathogens. 5

Health Stats Note the difference between the leading causes of death in the United States in 1900 and in 2000. Were any of the leading causes of death in 2000 infectious diseases? Explain why you think this is the case.

Bacterial Diseases There are thousands of infectious diseases, and over 40 kinds commonly occur in the United States. Four infectious diseases caused by bacteria are strep throat Lyme disease meningitis tuberculosis

Strep Throat “Strep” is short for Streptococcus, the bacterium that causes the disease. Strep bacteria, which are usually found in the nose and throat, can be spread by contact with mucus from an infected person. Symptoms include sore throat swollen lymph nodes on the sides of the neck headache fever

Lyme Disease Humans can become infected with the bacteria that cause Lyme disease when they are bitten by an infected tick. Symptoms of Lyme disease include a red rash at the site of the tick bite fever chills body aches The best way to protect yourself from Lyme disease is by avoiding tick bites.

Bacterial Meningitis An infection of the fluid in the spinal cord and the fluid that surrounds the brain is called meningitis. Symptoms of meningitis include high fever, headache, vomiting, and a stiff neck. There are two types of meningitis—one is caused by bacteria, the other by a virus.

Tuberculosis A highly contagious bacterial infection of the lungs is tuberculosis (too bur kyuh LOH sis), or TB. It is transmitted when droplets from an infected person’s cough or sneeze are inhaled. Symptoms, which include fatigue, weight loss, a mild fever, and a constant cough, may not show up for many years after the initial infection.

Treating Bacterial Diseases An antibiotic (an tih by AHT ik) is a drug that inhibits or kills bacteria. Using antibiotics exactly as they are prescribed is very important to prevent bacteria from developing resistance to the medicine. Antibiotic resistance can result if you don’t finish your prescription and some of the bacterial pathogens in your body survive.

Viral Diseases Viral diseases include the common cold influenza pneumonia hepatitis

The Common Cold The common cold is really a group of symptoms that is caused by a number of different viruses. One or two days after exposure to a cold virus, people develop sneezing sore throats runny noses coughing chest congestion fever headaches muscle aches Colds spread when a person touches a contaminated object or inhales droplets from a sneeze or a cough.

Influenza The flu, or influenza, is a common viral infection of the upper respiratory system. Influenza is spread by airborne droplets and contact with contaminated objects. High fever, sore throat, headache, and a cough are typical symptoms of the flu.

The Stages of the Flu

Pneumonia In people who are elderly, or who have heart disease or breathing problems, flu may develop into pneumonia (noo MOHN yuh), a serious infection of the lungs. Many people die each year from pneumonia, which can be caused by viruses, bacteria, or even fungi.

Hepatitis A group of viruses that infect the liver can cause hepatitis (hep uh TY tis), or inflammation of the liver. Symptoms of hepatitis include fever nausea pain in the abdomen jaundice (JAWN dis), or yellowing of the skin. Hepatitis A is transmitted in human wastes and in contaminated water and food. Hepatitis B can be transmitted in blood, during sexual contact, or during tattooing or body piercing. Hepatitis C can be transmitted in blood, during sexual contact, or during tattooing or body piercing.

Health Stats Note the difference between the leading causes of death in the United States in 1900 and in 2000. Were any of the leading causes of death in 2000 infectious diseases? Explain why you think this is the case.

Treating Viral Diseases In most cases, there is no particular medicine that can cure a viral infection. The best treatments for viral infections are rest, a well-balanced diet, and plenty of fluids. Many over-the-counter medicines can treat the symptoms of viral infections.

When to Seek Medical Care If you are worried about your health for any reason, see a doctor and discuss your concerns with him or her. Seek professional medical care if you have an extremely sore throat, earache, vomiting, diarrhea, or a temperature of 101°F that lasts more than two days mucus from your nose or throat that is thick and yellowish green difficulty breathing, or severe pain anywhere a cut, scrape, or sore that does not seem to be healing as it should an illness that lasts longer than usual

Preventing Infectious Diseases Here are some healthful behaviors you should practice to help you avoid disease. Wash your hands several times a day, especially before eating and after using the bathroom. Do not share items that can transfer pathogens, such as towels, eating utensils, cups, or hairbrushes. Cook and store foods properly. Meats should be cooked thoroughly. Hot foods should be kept hot, and cold foods should be kept cold. Avoid close contact with people who are ill.

Preventing Infectious Diseases Here are some healthful behaviors you should practice to help you avoid disease. Stay home when you are not feeling well. Learn to manage stress in healthful ways, and get at least eight hours of sleep each night. Eat well-balanced meals, and do not skip meals. Exercise regularly, at least three or more times a week. Avoid unhealthful substances, such as tobacco, alcohol, and illegal drugs.